Electromagnetic-dual-gradient laser-induced graphene/Fe₃O₄ composites with synergistic gradient-patterning for advanced electromagnetic interference shielding

The increasing prevalence of electromagnetic interference (EMI) demands shielding materials that offer strong attenuation with minimal reflection. While conventional metal-based shields suffer from high density, corrosion, and reflection-dominated mechanisms, we present a facile, scalable, and customizable route to fabricate laser-induced graphene/Fe₃O₄ gradient composites (LIG/Fe₃O₄) integrated with frequency-selective surface (FSS) patterning. Through decoupled control of electrical conductivity (via laser parameters) and magnetic permeability (via Fe₃O₄ loading), a multilayered gradient architecture is constructed, enabling progressive impedance matching and synergistic conductive-magnetic loss. The optimized composite exhibits exceptional total EMI shielding effectiveness (SE_T > 54 dB) in the Ku-band while maintaining low reflection loss (SE_R < 10 dB), yielding a remarkable specific shielding effectiveness (SSE/t) > 1391 dB·cm²/g. FSS further enhances localized field interactions, boosting absorption and overall performance. The synergy between the dual-gradient structure and surface patterning is elucidated, illustrating how independent property tuning collectively elevates shielding performance. With excellent flexibility, environmental stability, and flame retardancy, this work provides a versatile design platform for next-generation flexible electronics and advanced communication systems.